1. Field of the Invention
The invention relates to the field of optical sensors.
2. Background Information
Optical sensors in sensor systems contain a transmitter unit and a receiver unit linked to one another via an optical distance. Changes in the ambient conditions of the sensor can lead to a change in the optical distance and hence to a variation in the reception signal that can be detected and processed by an evaluation unit of the sensor system. In motor vehicles, for example, the changes in the optical properties caused by precipitation on the windshield can be registered by a sensor system, and the windshield wipers can be actuated.
To permit dependable recording of changes in the optical properties, the sensor system must be set to a defined initial value--for example by predetermining the transmission current or by adjusting the evaluation circuit. When the sensor system is used under changed ambient conditions--in the above example of the precipitation sensor with a different windshield type being used--the sensitivity of the optical sensor must be adjusted to the changed optical properties. To do so, either the amplification of the transmitter or that of the receiver must be varied by manual adjustment. In the case of frequently changing ambient conditions, this is very expensive for series production and entails high costs, since for every intended application a correspondingly adjusted system must be provided.